1. Field of the Invention
The present invention relates to a device securable on a screw-driving power tool for holding and supporting a fastening element insertable in a tool bit of the power tool, with the holding device including at least two clamping members which abut a stem of the fastening element in a support position of the clamping members and which are displaceable upon an application of a force thereto into their release position.
2. Description of the Prior Art
Holding devices of the type described above provide for an automatic retention of fastening elements in a screw-driving power tool and, thereby, noticeably facilitate the driving-in process. Because the holding devices support screws radially and, thereby, prevent wobbling of the screws and the resulting damage of the surfaces the screws are driven through, the holding devices are particularly advantageous for securing elongate self-drilling screws to sensitive surfaces, e.g., lacquered sheet metal of sandwich elements such as used in, e.g., shop-window constructions and in sheet metal roofs. In addition, the use of a holding device permits to dispense with a time-consuming, preliminary boring in many cases. In summary, holding devices permit to simplify the screw-in process and to prevent damage of constructional components and workpieces.
German Publication DE-4037547 discloses a device for holding screws that are secured in a screw-driving power tool with a sleeve-shaped component. A likewise sleeve-shaped support part is telescopically displaced over the sleeve-shaped component and carries two clamping members rotatable about respective pins. The clamping members are formed as holding jaws and extend, in the off-position, transverse to the inner wall, projecting inwardly therefrom, with the free ends of the holding jaws supporting the stem of a fastening element. Upon the screw being driven in, the front side of the support part, which faces the operational or drive-in direction, abuts the workpiece in which the screw is being driven. Upon continuation of the screw-in process, the support part is displaced by the counter-pressure of the workpiece relative to the sleeve-shaped component and relative to the screw. With the displacement of the support part relative to the screw, the screw head passes past the holding jaws, pivoting them in the direction of the workpiece and out of the drive-in path of the screw.
In order to insure that the screw can be driven into the workpiece up to a stop, it is necessary that the holding jaws be displaced, in the drive-in direction, completely behind the end surface of the tool bit of the screw-driving tool. The drawback of the foregoing procedure consists in that, among others, the displacement length of the support part relative to the sleeve-shaped component should correspond to the length of the holding jaws. As a result, it is necessary to use a special extension for connecting the spindle of the drive-in tool with the tool bit or to produce a special, elongate tool bit. Both solutions are associated with additional manufacturing costs.
Moreover, the known solution cannot be used for driving-in screws with large head or large plain or sealing washer. In this case, particularly long holding jaws should be used which, in turn, would require a particularly long displacement length and, therefore, a particularly unwieldy length of the holding device. Moreover, the production of such long holding jaws is relatively expensive, as they should insure an adequate stability during the support of the screw.
A further drawback of the known device follows from the sleeve-shaped construction of the components which provide a very limited view of a screw. Moreover, the components have a relatively large weight which, with the arrangement of the device at the front end of the screw-driving tool, leads to an unfavorable weight distribution and, as a result, to a poor handling of the screw-driving tool. In particularly, during the driving-in of the screw in a facade, a poor balance of a screw-driving tool is a hindrance.
Accordingly, an object of the present invention is to provide a holding device for screws in which the foregoing drawbacks are eliminated.
Another object of the present invention is to provide a holding device for screws having a simpler construction resulting from a reduced length of the holding device.